Ionomer for use in fuel cells and method of making same

ABSTRACT

The reaction product of a monomer comprising phthalazinone and a phenol group, and at least one sulfonated aromatic compound. The monomer comprising phthalazinone and a phenol group is used in a reaction with the sulfonated aromatic compound to produce ionomers with surprising and highly desirable properties. In one embodiment, the inventive ionomer is a sulfonated poly(phthalazinone ether ketone), hereinafter referred to as sPPEK. In another embodiment, the inventive ionomer is a sulfonated poly(phthalazinone either sulfone), herein after referred to as SPPES. In another embodiment, the inventive ionomer is other sulfonated aromatic polymeric compounds. The invention further includes the formation of these polymers into membranes and their use for polymer electrolyte membrane fuel cells (PEMFC), and in particular for direct methanol fuel cells (DMFC). The inventive polymers may be manufactured in membrane form, and can be dissolved into solution and impregnated into porous substrates to form composite polymer electrolyte membranes with improved properties.

FIELD OF THE INVENTION

This invention relates to an ionomer and its use as an electrolyte orelectrode component in a fuel cell, and particularly in a directmethanol fuel cell (DMFC).

BACKGROUND OF THE INVENTION

Solid polymer electrolytes or films have been well known in the art formany years. These polymers are typically characterized by high ionicconductivity, herein defined as greater than 1×10⁻⁶ S/cm. Such highconductivity values make them valuable where rapid transport of ionicspecies, for example, protons, is useful, for example in fuel cells.Additionally, it is desirable for such ionically conducting polymers tobe made in the form of membranes or thin films. In so doing, theresistance to ionic transport, which is a function of the filmthickness, can be reduced. These materials must also function in thetemperature range of interest, which can vary from below roomtemperature up to a large fraction of the melting temperature of thepolymer, depending on the application. Additionally, the polymer must berobust mechanically, so that it does not crack, either duringinstallation in a fuel cell, or during use.

The use of ionomers as solid polymer electrolytes in fuel cells is wellknown, having been developed in the 1960s for the US Gemini spaceprogram. Historically, the industry has moved from phenol sulfonicmaterials, which suffered from poor mechanical and chemical stability;to polystyrene sulfonic acid polymers, which have improved mechanicalstability, but still suffer chemical degradation; topoly(trifluoro-styrene)sulfonic acid, which has improved chemicalstability, but poor mechanical stability; to perfluorinated sulfonicacid materials (commercially available as NAFION® membranes), which hasimproved mechanical and chemical stability [e.g., see A. J. Appleby andF. R. Foulkes, Fuel Cell Handbook, Van Nostrand Reinhold, New York,1989; Table 10-1, pg. 268].

The perfluorinated sulfonic acid materials, for example those disclosedin U.S. Pat. No. 3,282,875, U.S. Pat. No. 4,358,545 and U.S. Pat. No.4,940,525, are still far from ideal ionomers. These materials must behydrated to conduct protons at an acceptable rate. As a result, in dryconditions or at temperatures above 100 degrees C., they work poorly inhydrogen-oxygen or hydrogen-air fuel cells. Furthermore, thesefluoropolymer ionomers are expensive to produce because of theinherently high cost of the fluorinated monomers required for theirpreparation. Finally, as more fully described below, they tend to have ahigh permeability to methanol, and therefore are inefficientelectrolytes for use in direct methanol fuel cells.

These limitations have led to the development of several classes ofionomers that are not substantially fluorinated, but rather are basedupon aromatic or linear polymers. In U.S. Pat. No. 4,083,768 apolyelectrolyte membrane is prepared from a preswollen membranecontaining an insoluable cross-linked aromatic polymer. Although thesemembranes have low ionic resistance, the controlled penetration of thefunctional groups during preparation can make preparation difficult. InU.S. Pat. No. 5,525,436, U.S. Pat. No. 6,025,085 and U.S. Pat. No.6,099,988 the preparation and use of polybenzimidizole membranes asionomers is disclosed. These polymers are described as particularlysuitable for use at temperatures above 100 degrees C. U.S. Pat. No.6,087,031 discloses a ionomer comprising a sulfonated polyethersulfonethat is suitable for use in a fuel cell. Kono et. al. discloses in U.S.Pat. No. 6,399,254 a solid electrolyte having a reduced amount ofnon-cross-linked monomer that can be rapidly cured through exposure toactive radiation and/or heat and has high conductivity. Finally, Wanget. al. have disclosed in WO 0225764 ionomers made by directpolymerization of sulfonated polysulfones or polyimide polymers.

Other substantially non-fluorinated ionomers are those in the class ofsulfonated Poly(aryl ether ketone)s. It is convenient to preparesulfonated poly(aryl ether ketone)s by post-sulfonation. However,post-sulfonation results in the placement of the sulfonic acid grouportho to the activated aromatic ether linkage, where the sulfonategroups are relatively easy to hydrolyze. Moreover, only one sulfonicacid per repeat unit can be achieved. To overcome this limitation, a newroute was developed to prepare sulfonated poly(aryl ether sulfone)s withmonomer containing sulfonate groups derived from sulfonating thedihalide monomer. Sulfonation of the dihalide monomer,4,4′-dihalobenzophenone and 4,4′dihalodiphenylsulfone, results insulfonic acid functionalization on both deactivated phenyl rings orthoto the halogen moiety, which offers them more chemical stability againstdesulfonation, and allows for two sulfonic acid groups per repeat unitof the resulting polymer. This approach displays other advantages,including being free from any degradation and cross-linking, and theability to easily control the content of sulfonate groups by adjustingthe ratios of the dihalide monomer to the sulfonated dihalide monomer.

In order to prepare ion exchange membrane for polymer electrolyte fuelcells (PEMFC) with excellent combined physical chemical properties andof low cost, attempts have been made by utilizing sulfonatedpoly(aromatic ether sulfone) and sulfonated poly(aromatic ether ketone).These membranes can be made by two methods. One is direct sulfonation ofpolymers, as reported in Polym. V28, P1009 (1987) wherein directsulfonation of poly(aromatic ether ketone) to prepare sulfonatedpoly(aromatic ether ketone) was reported. This method isstraightforward, but decomposition and crosslinking also occurred. Thedegree of sulfonation is also difficult to control. In addition, thesulfonated group directly attached to bisphenol-A could cause sulfonatedgroup be hydrolyzed and detached from the polymer structure afterprolong service at high temperature. Another method is to preparesulfonated monomers first, followed by polymerization afterwards.Macrom. Chem. Phy., (1997), P1421 (1998) reported this method. First,sulfonated difluoro-benzophenone was obtained by sulfonation ofdifluoro-benzophenone, then it was mixed with some difluoro-benzophenoneand bisphenol-A, followed by a copolymerization into sulfonatedpoly(aromatic ether ketone). The polymer structure is characterized bythe following structure:

The polymerization process does not induce decomposition or crosslinkingside reactions and it could control degree of sulfonation. The sulfonicacid groups located on the aromatic ring structure derived frombenzophenone are much more stable than the ones on bisphenol-A rings.However, because of the existence of methyl group in the polymerstructure, its anti-oxidation property is reduced. Furthermore, as thecontent of sulfonated group increases, swelling in water becomes verysevere.

Recently, bisphenol A-based and phenolphthalein-based and4,4′-thiodiphenol-based sulfonated poly(aryl ether ketone)s wereprepared by another method. Generally, most homogeneous ionomers havethe problem of large swelling degree at compositions where they havereasonable conductivity. So other components are blended with thepolymer in order to obtain ionomer membranes with lower swelling.

One issue with many of these polymers is that the ionic conductivity isnot as high as desirable. A high ionic conductivity in an ionomer isdesirable because the higher the ionic conductivity, the lower the cellresistance when the polymer is used as the electrolyte in a fuel cell.Because lower cell resistance leads to higher fuel cell efficiency,lower resistance (or high conductance) is better. One approach toreducing the resistance of these ionomers is to reduce its thickness, asthe resistance is directly proportional to thickness. Unfortunately,these ionomers cannot be made too thin because as they become thinner,they become more susceptible to physical or chemical damage, eitherduring cell assembly or cell operation. One approach to deal with thisissue has been disclosed in RE 37,707, RE 37,756 and RE 37,701 whereultra-thin composite membranes comprising expandedpolytetrafluoroethylene and an ion exchange material impregnatedthroughout the membrane are disclosed. Composite ionomer membranes arealso disclosed in U.S. Pat. No. 6,258,861.

One further complication in the use of ionomers as solid polymerelectrolytes in fuel cells is the need for the electrolyte to act as animpermeable barrier to the fuel. Should the fuel permeate through theelectrolyte it reduces cell efficiency because the fuel that permeatesthrough the electrolyte is either swept away into the outlet gas streamor chemically reacts on the oxidant side, giving rise to a mixedpotential electrode. In either case, the fuel is not used for producingelectricity. Furthermore, the fuel that permeates through theelectrolyte may also poison the catalyst on the oxidizing side, furtherreducing the cell efficiency. This issue, called fuel crossover, is aparticular problem when methanol is the fuel.

Methanol crossover rates tend to be high in many solid polymerelectrolytes because the methanol absorbs and permeates in the polymerin much the same way that water molecules do. Since many solid polymerelectrolytes transport water easily, they also tend to transportmethanol easily. One approach to reducing methanol crossover is tosimply use thicker membranes because the methanol transport-resistance(as defined below) increases with increasing thickness. This solutionhas limited utility, though, because as the thickness increases theionic resistance of the membrane increases as well. Higher ionicresistance in the membrane is detrimental to fuel cell efficiencybecause it results in higher internal resistance and thus higher (iR)power losses. Therefore, the ideal membrane for direct methanol fuelcells would be one that has both very high methanol transport resistanceand at the same time, has low ionic resistance. The combination of thesetwo characteristics would allow the use of thicker membranes, leading tolow iR power loss due to membrane resistance, while simultaneouslyminimizing the effect of methanol crossover.

The use of various polymers has been suggested to circumvent thismethanol crossover issue. In WO 96/13872 the use of polybenzimidazole issuggested for direct methanol fuel cells. In WO 98/22989, a polymerelectrolyte membrane composed of polystyrene sulfonic acid (PSSA) andpoly(vinylidene fluoride) (PVDF) is reported to have low methanolcrossover. In WO 00/77874 and U.S. Pat. No. 6,365,294 sulfonatedpolyphosphazene-based polymers are proposed as suitable ionomers fordirect methanol fuel cells. Finally, poly(arylene ether sulfone) hasbeen reported to have low methanol permeability [Y. S. Kim, F. Wang, M.Hickner, T. A. Zawodinski, and J. E. McGrath, Abstract No. 182, TheElectrochemical Society Meeting Abstracts, Vol. 2002-1, TheElectrochemical Society, Pennington, N.J., 2002]. Despite theseattempts, a need still exists for an ionomer with lower methanolcrossover rates and acceptably high ionic conductivity.

It is thus an object of this invention to satisfy the long-felt need forimproved ionomers for use as a polymer electrolyte membrane and as anelectrode component in fuel cells. It is also an object of the presentinvention to provide an improved method of forming a fuel cell using theinventive polymers. It is a further object of the invention to form acomposite solid polymer electrolyte with improved properties comprisingthe inventive polymers and a support. It is yet another object of theinvention to improve performance of a direct methanol fuel cellcomprising the inventive polymers. Finally, it is also an object of thenew invention to provide a fuel cell wherein the electrode comprises theinventive polymer.

SUMMARY OF THE INVENTION

This invention involves the reaction product of a monomer comprisingphthalazinone and a phenol group, and at least one sulfonated aromaticcompound. The monomer comprising phthalazinone and a phenol group isused in a reaction with the sulfonated aromatic compound to produceionomers with surprising and highly desirable properties. In oneembodiment, the inventive ionomer is a sulfonated poly(phthalazinoneether ketone), hereinafter referred to as sPPEK. In another embodiment,the inventive ionomer is a sulfonated poly(phthalazinone ether sulfone),herein after referred to as sPPES. In another embodiment, the inventiveionomer is other sulfonated aromatic polymeric compounds. The inventionfurther includes the formation of these polymers into membranes andtheir use for PEMFC, and in particular for DMFC. The inventive polymersmay be manufactured in membrane form, and can be dissolved into solutionand impregnated into porous substrates to form composite solid polymerelectrolytes with improved properties.

In one aspect, this invention provides an ionomer comprising thereaction product of monomer A (see below) with monomers B and C (alsobelow), wherein the moles of monomers B plus C equal the moles of A,wherein R₁₋₄ are independently H, linear or branched alkyl, aromatic, orhalogen; X₁ and X₂ are independently a carbonyl or sulfone radical oraromatic compounds connected through a ketone or sulfone linkage; Y isindependently a halogen group, and M is an alkali metal.

In another aspect, this invention provides an ionomer comprising thereaction product of monomer A with monomer B and C in an azeotropingsolvent mixed with an inert aprotic polar solvent containing at least 2moles of an alkali metal base for each mole of monomer A, wherein themoles of monomers B plus C equal the moles of A, said reaction driven tocompletion by the azeotropic removal of water at a temperature above theazeotropic boiling point of the azeotroping solvent in the presence ofwater, wherein R₁₋₄ are independently H, linear or branched alkyl,aromatic, or halogen; X₁ and X₂ are independently a carbonyl or sulfoneradical or aromatic compounds connected through a ketone or sulfonelinkage; and Y is a halogen group.

In another aspect, this invention provides an ionomer comprising thereaction product of monomer A with an ionomer-contributing monomer.

In another aspect, this invention provides a method of preparing asulfonated poly(phthalazinone ether ketone) comprising the steps of

-   (a) copolymerizing 4,4′-dihalo(or dinitro)-3,3′-disulfonate salt of    benzophenone, dihalo(or dinitro)benzophenone, and a monomer    containing phthalazinone and phenol group, in polar solvents or    reaction medium containing mainly polar solvents, in the presence of    a catalyst comprising a metallic base (or its salt), to obtain a    product;-   (b) dehydrating the product at high temperature using azeotropic    dehydration agents;-   (c) diluting the product with solvents;-   (d) coagulating the product using coagulation agents;-   (e) separating the product;-   (f) drying the product; and-   (g) performing steps (c) through (f) two additional times to obtain    the sulfonated poly(phthalazinone ether ketone).

In another aspect, this invention provides a method of preparing asulfonated poly(phthalazinone ether sulfone), comprising the steps of

-   (a) copolymerizing 4,4′-dihalo(or dinitro)-3,3-disulfonate salt of    phenyl sulfone, dihalo(or dinitro)phenyl sulfone, and a monomer    containing phthalazinone and phenol group, in polar solvents or    reaction medium containing mainly polar solvents, in the presence of    a catalyst comprising a metallic base (or its salt), to obtain a    product;-   (b) dehydrating the product at high temperature using azeotropic    dehydration agents;-   (c) diluting the product with solvents;-   (d) coagulating the product using coagulation agents;-   (e) separating the product;-   (f) drying the product; and-   (g) performing steps (c) through (f) two additional times to obtain    the sulfonated poly(phthalazinone ether sulfone).

In another aspect, this invention provides a method for generatingelectricity comprising the steps of:

-   -   (a) providing an anode;    -   (b) providing a cathode;    -   (c) providing a polymer electrolyte membrane between the anode        and the cathode and in communication with the anode and the        cathode, the polymer electrolyte membrane comprising the ionomer        of claim 1 in acid form    -   (d) flowing a fuel to the cathode where the fuel is        disassociated to release a proton and an electron;    -   (e) transporting the proton across the polymer electrolyte        membrane to the anode; and    -   (f) collecting the electron at a collector to generate        electricity.

In other aspects, this invention provides a polymer electrolyte membranecomprising the inventive ionomer, a membrane electrode assemblycomprising the inventive ionomer, and a fuel cell, particularly a directmethanol fuel cell, comprising the inventive ionomer.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross-sectional view of a membrane formed from an ionomeraccording to an exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of a composite membrane formed using anionomer according to an exemplary embodiment of the present invention.

FIG. 3 is a cross-sectional view of a membrane electrode assembly formedusing a solid polymer electrolyte according to an exemplary embodimentof the present invention.

FIG. 4 is a cross-sectional view of a fuel cell including a solidpolymer electrolyte according to an exemplary embodiment of the presentinvention.

FIG. 5 is a schematic of a room temperature conductivity fixture.

FIG. 6 is a schematic of a cell used to measure the permeance ofionomers to methanol solutions.

FIG. 7 is polarization curves comparing the results of hydrogen-air fuelcells using the inventive solid polymer electrolyte and two differentknown commercial materials.

FIG. 8 is polarization curves comparing the results of methanol-air fuelcells using the inventive solid polymer electrolyte and two differentknown commercial materials.

FIG. 9 is a scanning electron micrograph of a composite solid polymerelectrolyte as prepared in Example 7.

FIG. 10 is an infrared spectrum of the NAFION® 117 solid polymerelectrolyte membrane used in the Relative Selectivity Factormeasurement.

DETAILED DESCRIPTION OF THE INVENTION

The invention starts with a useful molecular structure, which lead topreparation of sulfonated poly(phthalazinone ether ketone)s in onepreferred embodiment. In this embodiment, the invention utilizessulfonated benzophenone and a monomer 4-(4-hydroxyphenyl) phthalazinone,which leads to introduction of phthalazinone structure into the polymer.Without being limited by theory, the pPhthalazinone group is believed tohave better high-temperature anti-oxidation properties than thebisphenol-A materials of prior art; also, the electron rich conjugatedhetero-cyclic nitrogen groups form hydrogen-bonding with sulfonic acidgroup, which increases crosslinking density of membrane materials, thusreducing swelling in water, which results in improvement of overallcombined properties for PEMFC applications.

More specifically, this embodiment of the invention utilizes monomers ofsulfonated dihalo(or dinitro)benzophenone, dihalo(ordinitro)benzophenone, and a monomer containing phthalazinone and phenolgroup to prepare copolymers of the novel sulfonated poly(phthalazinoneether ketone)s, characterized in the following structure:

wherein R₁ and R₂ are selected from hydrogen atom, alkyl group, oraromatic group; M is metallic base ion. The benzophenones used in thisembodiment of the invention are 4,4′-dihalo(or dinitro)benzophenones.The sulfonated benzophenones used in this embodiment of the inventionare 4,4′-dihalo(or dinitro)-3,3′-disulfonated salt of benzophenones. Themonomer containing phthalazinone and phenol group used in thisembodiment of the invention has the following molecular structure:

wherein R₁ and R₂ are selected from hydrogen atom, alkyl group, oraromatic group.

The monomer containing phthalazinone and phenol group may be producedaccording to methods taught in U.S. Pat. Nos. 5,237,062 and 5,254,663 toHay. Those patents do not, however, teach or suggest either the use ofthe phthalazinone monomer in a reaction with sulfonated aromaticcompounds, or the use of such products as ionomers or polymerelectrolyte membranes in fuel cells.

More broadly, the monomer containing phthalazinone and phenol groupuseful in the present invention comprises:

wherein R₁, R₂, R₃ and R₄ are independently selected from the groupconsisting of hydrogen, C1-C4 linear or branch alkyl group, or aromaticgroup. Examples include, but are not limited to

where Me is a CH₃ group and Ph is a phenyl group.

The unsulfonated and sulfonated aromatic monomers useful in thisinvention for reaction with the monomers above comprise compounds of thestructure:

respectively, where X₁ and X₂ are independently chosen from the groupconsisting of a ketone; a sulfone; or an aromatic compound connectedthrough a ketone or a sulfone linkage; and Y is a halogen group; and Mis an alkali metal. Examples of the unsulfonated aromatic monomerinclude, but are not limited to,

where in these latter three (the three in boxes) the bottom and topcompounds are connected at the —R linkage, i.e., the C═O directlyconnects the two rings, and Me is CH₃;

where Ph is a phenyl group. Examples of the sulfonated aromaticcompounds can be any of those shown above with an SO₃M group adjacent toeach halogen in the structure, where M is an alkali metal. The amount ofthe unsulfonated aromatic compound can be varied to change the EW of thefinal product during the reaction, and can range from 0 to about 95%.Overall, the combined number of moles of the unsulfonated and sulfonatedaromatic compounds should be equal to the number of moles of the monomercontaining phthalazinone and phenol group. It should be noted that theinventors intend this invention to encompass any ionomer formed bypolymerizing a monomer containing phthalazinone and phenol group withany ionomer-contributing monomer. The ionomer-contributing monomerpreferably comprises sulfonic acid or carboxylic acid.

In the reaction, the monomers are mixed with an azeotroping solvent andan inert aprotic polar solvent containing at least 2 moles of an alkalimetal base for each mole of the monomer containing phthalazinone andphenol group, and the reaction is driven to completion by the azeotropicremoval of water at a temperature above the azeotropic boiling point ofthe azeotroping solvent in the presence of water. The alkali metal baseis preferably an alkali metal hydroxide or an alkali metal carbonate.

This invention utilizes polymerization reaction temperature between150-200° C., reaction time 4-32 hours. The polymerization reaction canbe characterized by the following equation:

wherein R₁ and R₂ are selected from hydrogen atom, alkyl group, oraromatic group M is metallic base ion. It will be understood by thoseskilled in the art that the resulting structure shown above isrepresentative of the reaction product, but should not be construed tobe limiting. The product may have random, alternating or blocks of anyof the reactant monomers in any arrangement in the final product.

In one embodiment, the invention comprises the following polymerizationprocedures: equal molar ratio of (sulfonated benzophenone andbenzophenone) to the monomer containing phthalazinone and phenol group,metallic bases or excess 100% of metallic base salts, certain amount oftoluene (xylene or chloroform), certain amount of polar solvents, suchas dimethyl sulfoxide, tetramethylene sulfone, phenyl sulfone,1-methyl-2-pyrrolidinone, and N,N-dimethylformamide, were charged to a3-necked bottle. The bottle is equipped with nitrogen gas supply,cooling condenser, and mechanical agitator. Under the protection ofnitrogen blanket, the reaction medium was heated to dehydration. Thewater was removed by azeotropic boiling with azeotropic dehydrationagents, heating temperature up to 150-220° C., with 4-32 hours ofpolymerization time. After natural cooling, the desired reaction productwas isolated by repeating the following purification procedure threetimes: dilution with some solvents, coagulated, filtered, and dried. Thedesired products were characterized by measuring their viscosity andother physical properties.

This invention prepares polymers confirmed by infrared (IR) spectrum andneutron magnetic resonance (NMR) spectrum. Through adjustment ofsulfonated monomer ratio, reaction temperature and reaction time,several different desired products can be made with various sulfonatedcontent and different viscosity.

This invention prepares high molecular weight of novel sulfonatedpoly(phthalazinone ether ketone)s, having good properties, suitable forPEMFC applications. The membrane materials of this invention aresuperior to those based on other poly(aromatic ether ketone)s of priorart, in terms of resistance to high temperature oxidation properties,and they have low swelling in water. This material can be processed intofilms by dissolution in N,N-dimethylformamide, followed by casting anddrying of the wet film. The dried film has very good mechanicalproperties. The good mechanical properties are characterized by thereference teaching in U.S. Pat. No. 4,320,224. A 0.2-millimeter thickfilm, made by solvent casting and drying, can be folded at least fivetimes with 180° folding angle. If the folded film has no breakingcharacter, the resin is considered having good mechanical properties.Our invented resin has such good mechanical properties. This inventioncould conveniently adjust the sulfonated monomer ratio to change thesulfonated content in the products, which could adjust electronicconductivity and other properties of the products.

In addition to the use of poly(pthalazinone ether ketone)s describedabove, an alternative embodiment of the present invention producespoly(pthalazinone ether sulfone)s containing the monomer containing thephthalazinone and phenol group. In this embodiment, the phenyl sulfonesused are 4,4′-difluoro (chloro, bromo, or dinitro)phenyl sulfones. Thesulfonated phenyl are 4,4′-difluoro (chloro, bromo, ordinitro)-3,3′-disulfonated salt of phenyl sulfones. The monomercontaining phthalazinone and phenol group has the following molecularstructure:

wherein R₁ and R₂ are selected from hydrogen atom, C1-C4 linear orbranch alkyl group, or aromatic group.

In this embodiment the invention utilizes polymerization reactiontemperatures between 140-220° C., reaction time 1-36 hours. It utilizessolvents for polymerization medium, which includes polar solvents suchas dimethyl sulfoxide, tetramethylene sulfone, phenyl sulfone,1-methyl-2-pyrrolidinone, N,N-dimethylformamide; and uses water andmethanol (or ethanol) as coagulation agents.

This embodiment has the following polymerization procedures: Equal molarratio of (sulfonated phenyl sulfone and phenyl sulfone) to a monomercontaining phthalazinone and phenol group, certain amount of metallicbase or metallic base salts, toluene (xylene or chloroform), andsolvents were charged to a 3-necked bottle. Under the protection ofnitrogen blanket, the reaction medium was heated to dehydration. Thedehydrated water was removed by azeotropic boiling with azeotropicdehydration agents, heating temperature up to 140-220° C., with 1-36hours of polymerization time. After natural cooling, the desiredreaction product was isolated by repeating the following purificationprocedure three times: dilution with some solvents, coagulated,filtered, and dried. The desired products can be characterized bymeasuring their physical chemical properties.

This embodiment can be shown by the following polymerization equation:

wherein R₁ and R₂ are selected from hydrogen atom, C1-C4 linear orbranch alkyl group, or aromatic group, M is sodium or potassium ion, Xis fluorine, chlorine, bromine, or nitro —NO₂ group and m+n.> or =20. Itwill be understood by those skilled in the art that the resultingstructure shown above is representative of the reaction product, butshould not be construed to be limiting. The product may have random,alternating or blocks of any of the reactant monomers in any arrangementin the final product.

The inventive so-prepared polymers are confirmed by infrared (IR)spectrum and neutron magnetic resonance (NMR) spectrum. Throughadjustment of sulfonated monomer ratio, reaction temperature andreaction time, several different desired products can be made withvarious sulfonated content and different viscosity. It results inadjustment of electronic conductivity and other properties. Thisinvention prepares high molecular weight of novel sulfonatedpoly(phthalazinone ether sulfone)s, which is a novel ion exchangemembrane material. The membrane materials of this invention are superiorto those based on other poly(aromatic ether sulfone)s of prior art, interms of low swelling in water and resistance to high temperatureoxidation properties. This material can be processed into films bydissolution in N,N-dimethylformamide, followed by drying the wet film.The dried film has very good mechanical tensile strength and otherproperties.

As disclosed herein, the reaction product of combining a monomercomprising phthalazinone and phenol groups with at least one monomer ofa sulfonated aromatic compounds imparts surprising and desirableproperties to the resulting product, particularly for use in polymerelectrolyte fuel cells. One well skilled in the art will recognize thata wide range of sulfonated aromatic compounds can be used with saidphthalazinone monomer to produce desirable products. Comonomers of theunsulfonated versions of these sulfonated monomers may also be presentin the reaction. Reactions conditions such as reaction temperatures,dehydration agents and coagulation agents may vary depending on theparticular sulfonated aromatic compound, but are readily determined byone skilled in the art from the known properties of the monomer or itsunsulfonated cousin.

The polymers disclosed herein can be formed into a membrane 10 (as shownin the exemplary embodiment depicted in FIG. 1) using methods well knownin the art, including solution casting or dry pressing. The ease withwhich the polymer dissolves in aprotic dipolar organic solvents such asDMSO makes solution casting the preferable method.

One important parameter used to characterize ionomers is the equivalentweight. Within this application, the equivalent weight (EW) is definedto be the weight of the polymer in acid form required to neutralize oneequivalent of NaOH. Higher EW means that there are fewer active ionicspecies (e.g., protons) present. If it takes more of the polymer toneutralize one equivalent of hydroxyl ions there must be fewer activeionic species within the polymer. Because the ionic conductivity isgenerally proportional to the number of active ionic species in thepolymer, one would therefore like to lower the EW in order to increaseconductivity. The polymers disclosed herein can be prepared with a rangeof EWs between about 300 and greater than 4000, with preferable EW inthe range of 400 to 1500. As is well known in the art, by varying theconcentration of the reactants, different equivalent weight products canbe formed. For example, in the exemplary embodiment where the sPPEKpolymer is produced, Table 1 shows the concentrations of 4.4°-dihalo(ordinitro)-3,3′-disulfonate salt of benzophenone [Monomer 2 in Table 1]and dihalo(or dinitro)phenyl benzophenone [Monomer 1 in Table 1] onewould use to produce various EW polymers using the procedures disclosedherein. In Table 1 a fixed concentration of phthalazinone monomer of 10moles would be used. TABLE 1* Monomer 1 Monomer 2 EW IEC Moles Molesg/eq meq/g 0.0 10.0 288 3.472 0.5 9.5 299 3.345 1.0 9.0 311 3.214 1.58.5 325 3.080 2.0 8.0 340 2.941 2.5 7.5 357 2.799 3.0 7.0 377 2.652 3.56.5 400 2.500 4.0 6.0 427 2.344 4.5 5.5 458 2.183 5.0 5.0 496 2.016 5.54.5 542 1.844 6.0 4.0 600 1.667 6.5 3.5 674 1.483 7.0 3.0 773 1.293 7.52.5 912 1.096 8.0 2.0 1120 0.893 8.5 1.5 1467 0.682 9.0 1.0 2160 0.4639.5 0.5 4240 0.236*Fixed concentration of phthalazinone monomer of 10 Moles

It has also been discovered by the inventors that the inventive polymersdisclosed herein can be incorporated into various components of fuelcells to form highly desirable products. For example, the inventivepolymers can be used as the solid polymer electrolytes in hydrogen-airor in a direct methanol fuel cell. Furthermore, they can be incorporatedinto a porous polymer substrate material to form thin, strong membranesas shown in the exemplary embodiment of FIG. 2, where substrate 20 andionomer 21 form a composite membrane 22. Substrates 20 can include, butare not limited to porous polyolefins, including polyethylene,polypropylene and polytetrafluoroethylene. Polytetrafluoroethylene is aparticularly desirable porous substrate because of its chemicalinertness and high melting temperature. Various methods of formingporous polytetrafluoroethylene are known in the art. One particularlypreferable porous polymer substrate is expanded polytetrafluoroethyleneas described in U.S. Pat. No. 3,953,566, incorporated by referenceherein in its entirety. Using the methods disclosed by Bahar et. al. inU.S. Patent RE 37,707, RE 37,756 and RE 37,701, all incorporated byreference in their entirety, a composite solid polymer electrolyte withhighly desirable properties can be formed.

Additionally, the incorporation of the inventive ionomer within theanode and cathode electrode structures is desirable. It offers thepotential for improved cell performance, both in power density andmethanol crossover barrier characteristics (with concomitant improvementin voltage and fuel efficiencies) in direct methanol fuel cells.

Fuel cell electrodes comprising the inventive polymers could be inkingbased, typically prepared by mixing appropriate amounts of the ionomerwith catalyst and solvents, producing a slurry or ink. This ink can thenbe applied directly onto a membrane or onto decal substrates that cantransfer the catalyst layer onto the membrane via standard hot pressingtechniques.

Fuel cell electrodes containing the above ionomer can also be preparedusing PTFE-bonded catalyzed gas diffusion electrode (GDE) architectures,in which the methanol transport resistant ionomer is used to impregnate(using brushing, casting, spraying, etc.) the PTFE-catalyst structure.Anodes and cathodes prepared using this ionomer are expected to improvethe methanol crossover barrier characteristics of the MEA as well as theelectrodic performance of the cell (when compared to NAFION® impregnatedelectrodes).

Additionally, methanol tolerant/insensitive cathodes can also beprepared with the ionomers. Such electrodes can increase the cellperformance and voltage efficiency in a DMFC cell as the crossed-overmethanol would not adversely affect the oxygen reduction activity of theair electrode. The high methanol permeation resistance of this polymermakes it suitable and advantageous for its selective incorporation aselectrode ionomer for DMFC cathode thus yielding an air electrode withmethanol tolerant/insensitive characteristics. When the ionomers used inthis patent are present in high enough ionomer/metal ratios toeffectively block/cover the Pt catalyst, then it is expected that thecathode cell will exhibit large methanol insensitivity due to the highmethanol permeation resistance of this polymer.

Methanol tolerant/insensitive cathodes can be prepared by pre-treatingthe electrocatalyst prior to electrode/ink making with a solution of theabove polymer. The pre-treatment could consist of effective mixing andcontacting of the ionomer solution and the catalyst phases and posteriorevaporation of the solvent, thus resulting in a Pt catalyst phaseeffectively covered with a “skin” of the methanol permeation resistantionomer. This pre-treated catalyst can be used to make cathodeelectrodes of diverse architectures using methods known in the art,including inking, gas diffusion electrodes, etc.

Another approach to prepare methanol tolerant/insensitive cathodes wouldconsist on preparing an ink with the above ionomer, solvent and catalystbut using high ionomer/metal ratio. The resulting dry-ink electrodewould have the Pt phase effectively “blocked” by the methanol permeationresistant ionomer.

Finally a methanol tolerant/insensitive cathodes with PTFE-bondedcatalyzed GDE architecture can be prepared by dipping the GDE into asolution of the above ionomer. The ionomer will then totally impregnateand saturate the structure thus totally and effectively covering the Ptphase.

The inventive polymers can be formed into membrane electrode assemblyusing various approaches known in the art, as shown in the exemplaryembodiment of FIG. 3 where the membrane electrode assembly 33 is formedfrom an electrolyte separator 32 and two electrodes 30 and 31. Theinventive polymer can be incorporated into one or more electrodescomprising the inventive polymers; and/or the electrolyte separatorcomprising the inventive polymers. One or more of the preceding MEAs canbe assembled into an operating fuel cell 43 as shown in the exemplaryembodiment of FIG. 4, where the MEA 33 is assembled with two gasdiffusion media 40 and 41 one or more of which may also compriseinventive polymers. In order to generate electricity, the fuel cell isconnected to an external load through leads 44 and 45. As is well knownin the art, multiple MEAs can also be assembled into a fuel cell stackby separating multiple MEAs with attached gas diffusion media 47 withbipolar plates. The resulting fuel cell can be used with a variety offuels and oxidizing atmospheres to generate electricity. Fuels mayinclude hydrogen; alcohols, including methanol or ethanol; or otherhydrocarbon fluids. Oxidizing atmospheres can include oxygen, air,hydrogen peroxide, or other fluids that are oxidizing with respect tohydrogen. Finally, the inventive ionomers can comprise the electrolyteseparator in an electrolysis cell where electricity is used to formproducts.

The following procedures were used to characterize the ionomers preparedaccording the above description.

Equivalent Weight

Ion-exchange capacity is measured herein by determining the equivalentweight as follows: A dry weight of 0.5-1.0 g of the polymer membrane inthe SO₃H form is dipped in 50 ml of saturated NaCl solution. Theresulting acid solution containing the polymer membrane is titrated with0.1 N NaOH solution. The equivalent weight is determined from the ionexchange capacity according to EW(g/Equivalent) = 1000/IEC where${{IEC}\quad\left( {{meq}\text{/}g} \right)} = \frac{\left\lbrack {{ml}\quad{NaOH} \times 0.1\quad N} \right\rbrack}{{Dried}\quad{Ionomer}\quad{Solid}\quad{Weight}\quad(g)}$Room Temperature Resistance

A membrane sample about 2 inches by about 3 inches in size was firstequilibrated at room conditions of 21 degrees C., 55% RH for 24 hrs. Itwas then immersed into a plastic beaker containing room temperaturedeionized water. Two measurements were taken over a 2 hours time period:the first one after 30 minutes and the second one at 2 hours. To takethe measurements the membrane sample was taken out of the water andpatted dry by paper tissues. The thickness was then measured immediatelyusing an MT60M Heidenhain (Schaumburg, Ill.) thickness gauge attached toa Heidenhain ND281B digital display. The gauge was mounted verticallyover a flat plate, and measurements were made at eight differentlocations on the sample, covering the corners and center of the sample.The spring-loaded probe of the gauge was lowered gently on the film foreach measurement to minimize compression. The mean of the eight valueswas used as the sample thickness. The ionic resistance of the membrane10 was then measured using a four-point probe conductivity cell shown inFIG. 5. The sensing probes 55 of conductivity cell 50 are approximatelyone inch long, and approximately one inch apart. A plexiglass spacer 51provides insulation between the current probes 54 and sensing probes 55.The cell is held together with nylon screws 52 and electrical contact ismade to the probes through holes 53. During the measurement, a 900 gweight (not shown) was loaded onto the cell to ensure good contact. Itwas found that the resistance value is independent of further pressureonto conductivity cell 50. The resistance was measured by connectingleads (not shown) through holes 53 using 10 mV AC amplitude at 1000 Hzfrequency applied by a Solartron SI 1280B controlled by ZPlot softwarewritten by Scribner Associates. Measurements were taken in thepotentiostatic mode. Under these conditions, the phase angle was foundto be insignificant throughout the measurement. The room temperatureionic conductivity in S/cm for each measurement was calculated from theformula $\sigma\frac{L_{2}}{R*L_{1}*D}$Where σ is the room temperature ionic conductivity, L₂ is distancebetween the sensing probes, here equal to 2.5654 cm, L₁ is the length ofthe sensing probe, here 2.5603 cm, D is the measured thickness of themembrane in cm, and R is the measured resistance in ohms. The membraneionic resistance, in ohm-cm², is calculated from the conductivity fromthe formula: $\rho = \frac{D}{\sigma}$The results showed that the room temperature ionic conductivity wasindependent of the soaking time between 30 minutes and 2 hours for allthe samples tested. The reported value is the average calculated fromthe two measurements.Methanol Transport Resistance

A methanol permeation apparatus was used to evaluate the methanoltransport resistance characteristics of the solid polymer electrolytes.

Membrane samples to be tested were soaked in DI water for a minimum of10 minutes prior to testing. The soaking step allowed the membranes toequilibrate in water and to pre-swell before being assembled in thetesting fixture. A 5-cm×7-cm membrane piece was then cut to fit thetesting fixture, shown schematically in FIG. 6. The membrane sample 61was mounted between two pre-cut 1-mil polyethylenenapthalene (PEN)gaskets 62. The gaskets were cut in order to leave an opened window of3-cm×3.5-cm corresponding to a testing area of 10.5 cm². The wetmembrane thickness of the testing area was immediately measured with aMitutoyo snap gauge (Model # 7301). Measurements were made at sixdifferent locations and the mean of the six values was used as thesample wet thickness.

The membrane-gasket assembly was then placed into the testing fixture 67with the opened window towards the outlet end of the cell. A 2M methanolfeed solution was introduced into the testing fixture in inlet channel63 at a flow rate of 5 ml/min while DI water was introduced into thetesting fixture in inlet channel 65 at a flow rate of 5 ml/min. Thetesting fixture was tilted a few times to assure that no air bubbleswere trapped into the flow channels and was then placed tilted, outletend up, in a water bath set at 60 degrees C. Both the methanol feedsolution and the water flush were fed through the testing fixture for aminimum of an hour to allow equilibration and to reach a steady statepermeation rate of methanol through the tested samples. During this 1hour of equilibration time, the methanol solution exited the testingfixture through outlet channel 64 while the water flush exited thetesting fixture through outlet channel 66. Both methanol and watereffluents were discarded during the equilibration time.

After one hour, the water effluent or water permeate 66 was then sampled4 times at intervals of 5 minutes. Each sample was collected into a 5 mlvial and analyzed for methanol concentration by a Perkin Elmer AutoSystem XL gas chromatograph.

Four standards were prepared: 80, 800, 4000 and 8000 PPM of methanol inwater. All standards were sampled twice by the gas chromatograph (GC) toobtain a calibration curve of methanol peak area versus PPM of methanol.Each water permeate sample was also sampled twice and the measuredmethanol peak area was converted into PPM of methanol by using thecalibration curve. The methanol feed concentration was also verified byGC after dilution 40-fold.

The total methanol permeability was calculated according to:${P_{total}\left( {{cm}^{2}\text{/}\sec} \right)} = {\frac{\left( {C_{perm}*V_{perm}} \right)}{A}*\frac{t}{\left( {C_{feed} - C_{perm}} \right)}}$

-   -   where:    -   C_(perm)=concentration of the permeate water (convert PPM from        GC to mol/cm³)    -   C_(feed)=concentration of the methanol feed (mol/cm³)    -   V_(perm)=water flow rate (cm³/sec)    -   t=wet thickness (cm)    -   A=testing area (cm²).

A total resistance was then calculated according to:R _(total)(sec/cm)=t/P _(total)

The sample methanol transport resistance was then calculated bysubtracting the testing fixture resistance from the total resistance,i.e.,R _(sample) =R _(total) −R _(cell).

The testing fixture was designed to minimize noise, to assure properflows and constant concentration over the testing area; however, part ofthe methanol transport resistance could be attributed to the testingfixture contribution and needed to be subtracted from the totalresistance measured. The testing fixture resistance, R_(cell), wasdetermined from testing NAFION® perfluorosulfonic acid membranes (1100EW) of three different thicknesses. The total resistance for these threesamples was plotted against membrane thickness and the fixtureresistance was extrapolated from the intercept of the linear curve fitof the data with the y-axis (for a zero thickness).

Relative Selectivity Factor

As described above, there are two different important characteristics ofmembranes for solid polymer electrolytes in direct methanol fuel cells:ionic resistance and resistance to methanol transport. In orderto'assess the combination of these two, a Relative Selectivity Factor(RSF) is defined as follows:${RSF} = \frac{\left( \frac{{\overset{\_}{\rho}}^{NAFION117}}{{\overset{\_}{R}}_{total}^{NAFION117}} \right)}{\left( \frac{{\overset{\_}{\rho}}^{test}}{{\overset{\_}{R}}_{total}^{test}} \right)}$where

-   {overscore (ρ)}^(NAFION117) and {overscore (ρ)}^(test) are the ionic    resistances of NAFION® 117, and the test sample, respectively,    averaged over at least three and at least two samples, respectively;-   {overscore (R)}_(total) ^(NAFION117) and {overscore (R)}_(total)    ^(test) are the methanol transport resistances of NAFION® 117, and    the test sample, respectively, averaged over at least three and at    least two samples, respectively.

The NAFION® 117 material used as the reference herein was characterizedusing an IR measurement performed using a DigiLab FTS 4000 Excaliber inhorizontal attenuated total reflectance (HATR) mode with a ZnSe crystal.The measurement used a resolution of 4 and 20 scans were co-added. Theresults of this measurement are shown in FIG. 10.

The RSF for the standard NAFION® 117 membrane is, by arbitrarydefinition, equal to one. Materials that have a lower ratio of ionicresistance to methanol transport resistance than the NAFION® 117membrane should be superior materials for direct methanol fuel cells.Such materials will thus have a RSF greater than one.

Electrochemical Methanol Crossover Measurement

This measurement was performed in a direct methanol fuel cell (DMFC)cell by evaluating the electrochemical limiting current originated byelectrooxidation of the methanol flux as described in X. Ren, T.Zawodzinski Jr., F. Uribe, H. Dai and S. Gottesfeld Electrochem. Soc.Proc. Vol 95-23 p.284 First Intl. Symp. on Proton Conducting MembraneFuel Cells I The Electrochemical Society (1995).

Briefly, the same MEA used for DMFC polarization performance is used forelectrochemical crossover. The air electrode or cathode is converted toa N₂ electrode. The anode is unchanged flowing methanol solution. Anexternal power supply or potentiostat is then used in bipolar mode(working electrode=N₂ electrode, counter/reference electrodes=methanol(fuel) electrode) to externally bias the cell. The electrooxidation ofcrossed-over methanol occurs in the N₂ electrode (working electrode)following the following redox reaction:

and the electroreduction of the proton flux to H₂:

takes place in the methanol electrode (counter/reference). Thesteady-state methanol electrooxidation current is then measured versusimposed cell potential (typically 0 to 1V): it increases with cellpotential and will typically reach a limiting value or plateau. Thislimiting current is then a measure of the methanol crossover rate, andits flux can be calculated from the following relationship:${F_{crossover} = \frac{i_{\lim}*1000}{6F}},$where i_(lim) is the measured limiting current density in mA/cm², F isthe Faraday's constant, equal to 96487 A-s/mol and F_(crossover) is inmicromol/cm²-s.

Specifically, the electrochemical methanol crossover measurement wasperformed on the cell using an externally biased Amel Instruments 2055High Power Galvanostat/Potentiostat in conjunction with and AmelProgrammable Function Generator (Model 568). The cell remained connectedto the same Globetech gas unit used for fuel cell polarizationexperiments described below in Characterization of Examples AndComparative Examples. The procedure for this test was as follows: thecell was potentiostatically biased in bipolar mode (working electrode=N₂electrode, counter/reference electrodes=methanol electrode) with cellpotential (working versus reference) spanning 0→900 mV, slowly scanningat 2 mV/sec. The slow scan rate was used to assure a steady-statecurrent measurement. The cell was held at 60 degrees C. with anodeflowing 2.5 ml/min of 1.0 M CH₃OH solution and cathode flowing 50 sccmof N₂ saturated at 65 degrees C. The heat trace lines to the cell wereheld at 75/70 degrees C. for anode and cathode, respectively. At leastthree scans were conducted to average a characteristic methanolcrossover limiting current, each scan conducted ca. 15 minutes apart toguarantee stabilization of the cell prior every measurement. Themethanol crossover was calculated as described above.

The following examples are intended to demonstrate but not to limit theinventive ionomers and methods of making them. Unless otherwisespecifically mentioned, the source of compounds used in the examples isas follows: 4,4′-Difluorobenzophenone was purchased from AldrichChemical Co. and used without further purification. 4-(4-Hydroxyphenyl)phthalazinone (supplied by Dalian University of Technology) was used asreceived. 5,5′-Carbonylbis(2-fluoro-benzene sulfonate) was synthesizedby sulfonation of 4,4′-difluorobenzophenone according to the generalprocedure reported by Wang [F. Wang, T. Chen, J. Xu, Macromol. Chem.Phys. 1998,199,1421]. Dimethyl sulfoxide (DMSO) and toluene werepurified by distillation and stored over 4A molecular sieves. Otherreagents and solvents were obtained commercially and used withoutfurther purification.

EXAMPLE 1 sPPEK Polymer Preparation

2.5338 gram (6 milli mole) of disodium3,3′-sulfonyl(4,4′-difluorobenzophenone), 5.2368 gram (24 milli mole) of4,4′-difluorobenzophenone, 7.1474 gram (30 milli mole)4-(4-hydroxyphenyl) phthalazinone and 3.1796 gram (30 milli mole) sodiumcarbonate, 40 milliliter of toluene, 60 milliliter of dimethyl sulfoxidewere charged to a 3-necked bottle, which equipped with nitrogen purgesupply, cooling condenser, and mechanical agitator. Under protection ofnitrogen blanket, the bottle was heated to 190° C. for 8-hour ofpolymerization. During the polymerization, water was generated and wasremoved by azeotropic boiling with toluene. After cooling, the reactionproduct was diluted with dimethyl sulfoxide, followed by coagulation by1:1 by weight of ethanol/water mixture. The coagulant was filtered threetimes, then dried in a vacuum oven at 80° C. The obtained product has areduced viscosity of 1.08 dl/g, glass transition temperature of 252° C.,and thermal weight loss of 10% at 532° C.

EXAMPLE 2 sPPEK Polymer Preparation

5.0675 gram (12 milli mole) of disodium3,3′-sulfonyl(4,4′-difluorobenzophenone), 3.9276 gram (18 milli mole) of4,4′-difluorobenzophenone, 7.1474 gram (30 milli mole)4-(4-hydroxyphenyl) phthalazinone and 3.1796 gram (30 milli mole) sodiumcarbonate, 40 milliliter of toluene, 60 milliliter of dimethyl sulfoxidewere charged to a 3-necked bottle, which equipped with nitrogen purgesupply, cooling condenser, and mechanical agitator. Under protection ofnitrogen blanket, the bottle was heated to 190° C. for 8-hour ofpolymerization. During the polymerization, water was generated and wasremoved by azeotropic boiling with toluene. After cooling, the reactionproduct was diluted with dimethyl sulfoxide, followed by coagulation by1:1 by weight of ethanol/water mixture. The coagulant was filtered threetimes, then dried in a vacuum oven at 80° C. The obtained product has areduced viscosity of 3.38 dl/g, glass transition temperature of 308° C.,and thermal weight loss of 10% at 497° C.

EXAMPLE 3 sPPEK Polymer and Membrane Preparation

An sPPEK solid polymer electrolyte was prepared as follows: In a 150 mlthree-necked round flask, equipped with a Dean-Stark trap, a condenser,a nitrogen inlet, 20 mmol 4-(4-Hydroxyphenyl)phthalazinone, a mixture of5,5′carbonylbis(2-fluorobenzene sulfonate) and 4,4′-difluorobenzophenone(20 mmol), and appropriate amount of alkali were added into a mixture of40 ml DMSO and 45 ml toluene. The mixture was refluxed for 3 h at 150 C,and then excess toluene was distilled off. The mixture was heated at 175C for 20 h. Then the reaction mixture was cooled to room temperature andpoured into water to precipitate the copolymer. The crude product wasthen washed six times with hot water to remove inorganic salts. Thepurified polymer was filtered and dried in vacuo at 100 C for 48 h. Theresulting polymer was sPPEK polymer shown above with R₁ and R₂ equal tohydrogen, and M equal to Na.

A membrane was prepared by casting a 3% solution in DMSO on a glassplate in a dust-free environment. The membranes were dried at 85 C for10 h and successively dried in a vacuum oven at 100 C for 48 h. Theresulting membrane was then ion exchanged to acid form. The EW of thepolymer as calculated from the constituents was 621 while that measuredexperimentally using the procedure described above was 633, which are inagreement within the experimental error. This agreement indicates thatthe pendant sulfonate groups were successfully attached to the polymerchains.

The Relative Selectivity Factor as described above was calculated forthe resulting solid polymer electrolyte membrane. The calculated RSF was1.28, indicating that the membrane is expected to show improved directmethanol fuel cell performance over the standard NAFION® 117 membranewhen used as a solid polymer electrolyte in a direct methanol fuel cell.

EXAMPLE 4 AND COMPARATIVE EXAMPLE A AND B Preparation of MEAs

In order to assess the inventive solid polymer electrolyte under fuelcell conditions, membrane electrode assemblies (MEAs) were prepared forboth the inventive solid polymer electrolyte in acid form of Example 3and two comparative examples, acid form of NAFION® membrane 117(Comparative Example A) and acid form of NAFION® membrane 112(Comparative Example B) available from E. I. Du Pont de NemoursCorporation. The two comparative examples are commercial materials ofperfluorosulfonic acid solid polymer electrolytes, where the equivalentweight is 1100. The two materials differ only in thickness, with NAFION®membrane 117 having a nominal thickness of 7 mils or 175 microns (actualthickness, 179 microns as measured using an MT60M Heidenhain(Schaumburg, Ill.) thickness gauge attached to a Heidenhain ND281Bdigital display), and NAFION® membrane 112 having a nominal thickness of2 mils or 50 microns (actual thickness 46 microns). The inventivepolymer had a measured thickness of 36 microns, when dry, as determinedusing an MT60M Heidenhain (Schaumburg, Ill.) thickness gauge attached toa Heidenhain ND281B digital display.

To prepare MEAs from the inventive solid polymer electrolyte and thecomparative examples, electrodes were prepared first. The same anode andcathode was used for both the inventive solid polymer electrolyte andthe comparative examples. Standard commercial electrodes impregnatedwith NAFION® 1100 EW ionomer solution were used. The procedure for theelectrode preparation was as follows. The anode was a commercial gasdiffusion electrode (GDE) purchased from E-Tek Inc. The GDE contained4.0 mg/cm² unsupported PtRuOx (Pt:Ru=1:1) and 10% PTFE in the catalystlayer and was applied onto non-wetproofed carbon paper gas diffusionmedia (EFCG/TGPH-060). The cathode was a commercial gas diffusionelectrode (GDE) purchased from E-Tek Inc. The GDE contained 4.0 mg/cm²Pt black and 20% PTFE in the catalyst layer and was applied onto singlesided ELAT gas diffusion media.

The electrodes were die-cut in 5 cm² squares (correspondent to the MEAactive surface area) and were individually impregnated with Nafionsolution (1100 EW) prior to MEA preparation. The anode and cathodeionomer impregnation levels were selected to be ca. 0.7 mg dryionomer/cm² and 0.3 mg dry ionomer/cm² for the anode and cathode,respectively, following a ratio of metal catalyst-to-ionomer in theanode and cathode of 5.7 and 13.3. The impregnation ionomer solution wasprepared from a master Nafion (1100 EW) solution 22% solids (E. I. DuPont de Nemours Corporation) which was diluted at a ratio of 1:4 with50% C₂H₅OH—H₂O solution. The diluted Nafion solution was then uniformlybrushed on the surface of the GDE, dried using a heat gun, and weighted.This process was repeated until the desired target ionomer loading wasachieved. The process typically took 2 to 3 passes to achieve the targetionomer loading.

Using the electrodes so prepared, an MEA was prepared for the inventivesolid polymer electrolyte and the two comparatives by standard hotpressing of the ionomer-impregnated GDEs to the electrolyte membrane.Pressing conditions were adjusted to achieve good bonding to the solidpolymer electrolyte. The electrode/membrane/electrode elements wereplaced between two pieces of Kapton tape and hot pressed in a manualpress (PHI, model Q230H, with heated platens). For the comparativeexamples, pressing conditions were 12 tons load, 320° F. (both platensheated) and 3 minutes pressing time. For the inventive example, 12 tonsload, 200° F. (both platens heated) and 3 minutes pressing time wasused.

EXAMPLE 4A Fuel Cell Preparation Using Inventive Solid PolymerElectrolyte and Comparative Solid Polymer Electrolytes

Fuel cells using the two MEAs having the comparative examples as solidpolymer electrolytes, and the one MEA using the inventive solid polymerelectrolyte were assembled using the following procedure. The MEA ofExample 4 (5 cm² active surface area) was loaded in a standard fuel celltesting fixture (5 cm², single channel serpentine flow field, 8 boltsmade by Fuel Cell Technologies, Alburquerque N. Mex.). The bolts werelubricated with Krytox lube (Du Pont) prior to assembly. The MEA wasassembled using commercial 7 mils silicon-impregnated glass cloth (TateEngineering, Aston, Mich.) gasket for the anode and 10 mils gasket forthe cathode. All gaskets had a 5 cm² window and covered the entiregraphite plate of the fuel cell fixture and membrane border of the MEA,typically 3 in×3 in. The assembly was conducted without alignment pinsin order to avoid gas leakage between plates. No additional gasdiffusion media was added. Upon alignment of the elements and assemblythe fixture was then torqued down to 45 lb-in/bolt compression following5 lb-in increments in a star configuration for the 8 bolts. Atorque-wrench (with maximum torque of 75 lb-in) was used to torque thecell to the desired load. Finally the cell was also checked forelectrical shorts between the current collector and compression platesprior to applying load at the fuel cell station.

EXAMPLE 5 Electrode Containing Inventive Ionomer

Prototype DMFC anode and cathodes were prepared using the samecommercial base (ionomer-free) electrodes and same ionomer impregnationstrategies used for the “screening”-Nafion based gas diffusionelectrodes (GDEs) described in Example 4.

A 3% solids dimethyl sulfoxide solution using the solid polymerelectrolyte membrane of Example 3 was prepared. An ionomer solution ofthe polymer was produced by dissolving a membrane in appropriatesolvents. Dimethyl sulfoxide (DMSO) was found to be a good solvent forsolution preparation. The ionomer membrane of Example 3 was first ionexchanged to the sodium form by neutralization with a 0.5N sodiumhydroxide solution. The membrane was allowed to dry at room temperaturefor a minimum of 4 hours. 8.9 g of methyl sulfoxide was poured into aflask. The solvent was agitated by a magnetic stirrer and the flask waskept under dry nitrogen. 0.3 g of membrane was then added to the flaskto prepare a 3% solids solution in DMSO. The content of the flask washeated to 90 degrees C. for about 30 minutes for complete dissolution ofthe membrane. The resulting ionomer solution, contained 3% solids.

This solution was then used to impregnate the 5 cm² GDEs resulting inprototype anodes and cathodes. The resulting anode GDE consisted ofunsupported 4.0 mg/cm² PtRuOx metal catalyst loading impregnated at alevel of ca. 0.7 mg/cm² dry ionomer. The prototype cathode GDE consistedof unsupported 4.0 mg/cm² Pt black metal catalyst loading impregnated ata level of ca. 0.3 mg/cm² dry ionomer. The impregnated electrodes werepost-dried in a vacuum oven overnight at 200 degrees C. to completelyeliminate the residual solvent. After the drying step all electrodeswere soaked in 3N HNO₃ to ion-exchange the polymer to the acid (H⁺)form. Finally, the electrode was rinsed in deionized water to remove anyexcess acid.

EXAMPLE 6 Electrode Containing Inventive Ionomer

Prototype methanol tolerant/insensitive cathodes were prepared using thesame commercial base (ionomer-free) electrodes (PTFE-bonded Pt blackbased GDEs) of Example 4. The 5 cm² electrodes were completely dipped ina solution described in Example 5 (3% solids) and gently stirred toallow total saturation and penetration of the polymer. Upon removal theexcess ionomer was wiped with a paper towel and the dipped electrodeswere post-dried in a vacuum oven overnight at 200 degrees C. tocompletely eliminate the residual solvent. The dried electrode wassoaked in 3N HNO₃ to convert the ionomer to acid (H⁺) form, and thenrinsed in excess de-ionized water to wash out the excess nitric acid.The prototype cathode GDE then consisted of unsupported 4.0 mg/cm² Ptblack metal catalyst loading saturated at a level of ca. 0.5 mg/cm² ofthe dry ionomer.

EXAMPLE 7 Composite Solid Polymer Electrolytes

A composite membrane was prepared as follows: a 3% solids dimethylsulfoxide solution was prepared using the solid polymer electrolyte ofExample 3, as described in Example 5. This solution was diluted in halfwith ethanol to prepare a 1.5% solids in a 50/50 dimethylsulfoxide/ethanol solution. This solution was then impregnated into a22-micron thick support of an expanded polytetrafluoroethylene (ePTFE)according to the teaching of Bahar, et. al. in U.S. Patent N0 RE37,307.The ePTFE was fixed in a 4-in embroidery hoop. The ionomer solution waspainted on both sides of the ePTFE support and then dried with a hairdrier to remove the solvents. The painting and drying steps wererepeated 4 more times. The ePTFE and the embroidery hoop were thenplaced into a solvent oven set at 190° C. for 10 minutes to completelyremove all solvent traces. The sample was then removed from the oven,allowed to cool to room temperature and finally taken off the embroideryhoop. The ePTFE/solid polymer electrolyte composite membrane wastransparent, indicating substantially complete impregnation of thesupport by the solid polymer electrolyte.

The SEM micrograph of FIG. 9 is a cross-sectional image of the resultingcomposite solid polymer electrolyte membrane. The solid polymerelectrolyte that acts herein as an ionomer is substantially impregnatedthroughout the porous microstructure of fibrils in the ePTFE as shown inthe composite layer 92.

EXAMPLE 8 sPPES Polymer Preparation

1.2834 gram (2.8 milli mole) of disodium 3,3′-sulfonylbis(4-fluorophenylsulfone), 1.0679 gram (4.2 milli mole) of bis(4-fluorophenyl)sulfone,1.6677 gram (7 milli mole) 4-(4-hydroxyphenyl) phthalazinone and 1.1609gram (8.4 mini mole) potassium carbonate, 30 milliliter of toluene, 20milliliter of tetramethylene sulfone were charged to a 3-necked bottle,which equipped with nitrogen purge supply, cooling condenser, andmechanical agitator. Under protection of nitrogen blanket, the bottlewas heated to 200° C. for 10-hour of polymerization. During thepolymerization, water was generated and was removed by azeotropicboiling with toluene. After cooling, the reaction product was dilutedwith tetramethylene sulfone, followed by coagulation in water. Thecoagulant was filtered three times, then dried in a vacuum oven at 100°C. The obtained product has a reduced viscosity of 1.74 dl/g, andthermal weight loss of 10% at 533° C.

EXAMPLE 9 SPPES Polymer Preparation

0.9625 gram (2.1 milli mole) of disodium 3,3′-sulfonylbis(4-fluorophenylsulfone), 1.2459 gram (4.9 milli mole) of bis(4-fluorophenyl)sulfone,1.6677 gram (7 milli mole) 4-(4-hydroxyphenyl)phthalazinone and 1.1609gram (8.4 milli mole) potassium carbonate, 30 milliliter of toluene, 20milliliter of tetramethylene sulfone were charged to a 3-necked bottle,which equipped with nitrogen purge supply, cooling condenser, andmechanical agitator. Under protection of nitrogen blanket, the bottlewas heated to 200° C. for 10-hour of polymerization. During thepolymerization, water was generated and was removed by azeotropicboiling with toluene. After cooling, the reaction product was dilutedwith tetramethylene sulfone, followed by coagulation in water. Thecoagulant was filtered three times, then dried in a vacuum oven at 100°C. The obtained product has a reduced viscosity of 1.45 dl/g, andthermal weight loss of 10% at 534° C.

Characterization Of Examples And Comparative Examples

To characterize the utility of the inventive polymer when used as asolid polymer electrolyte, the assembled fuel cell fixture of Example 4Awas connected to a fuel cell testing plant for cell diagnostics. Thefuel cell testing plant consisted of an electronic load, a gas-controlunit, methanol injection setup and ancillary equipment (condenser, gasline heat tracing, etc.) The electronic load was a Scribner & Assoc.(VA) 10 A model 890B-100 and was used for fuel cell mode H₂/air andmethanol/air polarization analysis. The electronic load box alsocontained standard temperature controllers for the cell and the reactanthumidifiers. The load interfaced with a PC running Scribner & Assoc.fuel cell software (version 3.1a) for data acquisition and analysis.

The basic gas unit was made by Globetech CMIX and after “in house”modifications consisted of 3 liter reactant humidifier bottles for H₂and air, both with independent temperature control. The station also hadmass flow controllers and back-pressure regulators for the gaseousreactants. The gas feeds could also be delivered humidified or dry tothe cell via a 3 way valve manifold. The cell is connected to this gasunit with its feeds heat traced and temperature controlled.

The methanol injection was done via a secondary manifold to the anodecell feed. The apparatus consists of a methanol solution reservoir (1liter 3-head Pyrex flask) in which a N₂ blanket was continuouslybubbled, a 2-syringe injection-withdrawn pump (Kd Scientific, model 210C) with flow control, and a 100 cc accumulation volume (to avoid flowfluctuations) placed in the injection manifold right before the cell.The injection setup could be isolated from the cell via an array ofon/off valves that allowed the switching from H₂ to methanol solution asthe anode fuel.

Once the fuel cell fixture was hooked up to the test station, the celltemperature was then set to 60 degrees C., the anode and cathode bottleswere set to 70 degrees C. and 65 degrees C., respectively. Theback-pressure was kept at 0 psig on both sides, and the heat-traces onthe gas lines were set to 75 and 70 degrees C. for anode and cathoderespectively. The hydrogen fuel was then supplied to the anode at a flowrate of 100 ml/min and the air was supplied at the cathode at a flowrate of 200 ml/min. Once the cell temperature had reached the set value,the cell was allowed to condition for a minimum of 6 hours. During thisconditioning time, the cell potential was potentiostatically cycledbetween 0.6V, 0.3V, and 0.8V in 0.2V potential step increments. As isgenerally practiced in the art, voltages are versus the hydrogen dynamicelectrode, i.e., flowing hydrogen gas at the anode with no separatereference electrode used. The cell was maintained at each step for a 5to 10 minutes time period. At the end of the fuel cell potentialcycling, the anode reactant and cathode reactant minimum flow rates weredropped to 20 ml/min and 40 ml/min, respectively, to allow for flow totrack the load (i.e., stoichiometric control). The cell was thenoperated under constant stoichiometry using 1.2× stoichiometry on theanode, and at 2.5× stoichiometry on the cathode. Stoichiometric flow isdefined as gas flow at any given current density such that the gas wouldbe completely consumed in the fuel cell reaction. The fuel cell wasagain cycled at least twice between 0.6V, 0.3V and 0.8V to reach steadystate under stoichiometric control mode. Finally, a polarization curvewas obtained by recording the steady state current after 5 to 10 minutesfollowing sequential voltages. The step increment was 0.1 V for thecomparative examples, and 0.05V for the inventive example. Thepolarization curve was started from 0.6V and potential steps were firsttaken towards lower voltages; then the cell was taken back to 0.6V toequilibrate and the potential steps were taken towards open circuitvoltage. The open circuit voltage (OCV) is defined as the maximumvoltage obtained from the trace of OCV versus time after the load isremoved from the cell. Additionally, at each potential the cellresistance was measured by using a standard current interrupt techniqueavailable through the Scribner Version 3.1a (Firmware Version 1.43)software used to control the system.

Once the polarization curve was completed, the fuel cell was shutdownfor the night and the cell, humidification bottles and heat tracetemperatures were dropped down to room temperature. The fuel cell wasre-started the next day according to the same start-up protocoldescribed above. The cell potential was again cycled between 0.6V, 0.3Vand 0.8V to condition the fuel cell. If the cell performance wascomparable to that of the first day, a second polarization curve wasrecorded to confirm the performance. If the cell performance was betteron the second day than the first day, then the cell was cycled for aminimum of four more hours and a polarization curve was obtained at theend of this conditioning period. The polarization curves obtained on thesecond day were used for MEA comparison and are reported in FIG. 7.

The fuel cell was then switched from hydrogen/air mode to methanol/airmode (direct methanol fuel cell or DMFC mode). The anode side of thefuel cell was first flushed with nitrogen and then a 1M-methanolsolution was pumped at 1 ml/min to the anode side using a Kd Scientificinjection-withdrawn pump. The cathode was switched to dry air and set ata flow rate of 100 ml/min. The fuel cell was cycled between 0.3V, 0.1Vand 0.6 V in 0.3 V potential steps to condition the MEA. The fuel cellwas maintained at each potential step for a 5 to 10 minutes time period.After cycling the cell in DMFC mode for a minimum of 3 hours, a DMFCpolarization curve was recorded in a similar fashion as reported before.In this case, the polarization curve was started from 0.3 V and thepotential was first lower to 0V in 0.05 V step increments; then the cellwas taken back to 0.3V and the potential was increased to open circuitvoltage, in 0.05 V step increment. The OCV was measured as describedabove.

The polarization results of the tests for hydrogen-air and methanol-airare shown in FIGS. 6 and 7 respectively. In hydrogen-air (FIG. 6), above˜0.75 V, the inventive polymer had fuel performance comparable to thecomparative examples, while at lower voltages, its fuel performance isbetween the two comparative examples, a surprisingly good result for anon-fluorinated polymer, particularly given the thickness of themembrane. In methanol-air (FIG. 7), the performance of the inventivesolid polymer electrolyte is superior to both comparative examples atall potentials. At 0.3V, the current density of the MEA prepared withthe inventive polymer is 80 mA/cm² while the current density of theNAFION 112 and the NAFION 117 based MEAs are 50 mA/cm² and 61 mA/cm²,respectively: a 60% and 31% performance improvement over NAFION® 112 andNAFION® 117 MEAs, respectively. Also, the measured open circuitpotential of 0.704 V for the inventive solid polymer electrolyte ofExample 3 is higher than either comparative example A, 0.683 V, orComparative Example B, 0.645, indicative of improved performance.

The results of an electrochemical methanol crossover measurement (Table2) indicate that the inventive solid polymer electrolyte has lowerelectrochemical methanol crossover than either Comparative Example A orB. This result is particularly surprising in that the inventive solidpolymer electrolyte is about five times thinner than Comparative ExampleA and still has lower crossover. TABLE 2 Electrochemical MethanolCrossover Measurement Comparative Comparative Example A: N117 Example B:N112 Example 4A Scan 1 0.138 0.322 0.129 Scan 2 0.136 0.315 0.127 Scan 30.120 0.289 0.116 Average 0.131 0.309 0.124 Stddev 0.009 0.017 0.007*Results reported in units of micromole/cm²-sec

The examples and specific embodiments presented herein are intended toillustrate the invention but not to limit it in any way. Rather, thescope of the present invention is embraced by the following claims.

1. An ionomer comprising the reaction product of monomer A with monomerB and C, wherein the moles of monomers B plus C equal the moles of A,wherein R₁₋₄ are independently H, linear or branched alkyl, aromatic, orhalogen; X₁ and X₂ are independently a carbonyl or sulfone radical oraromatic compounds connected through a ketone or sulfone linkage; Y isindependently a halogen group, and M is an alkali metal.


2. An ionomer as defined in claim 1 wherein monomer A comprises4-(4-hydroxyphenyl)phthalazinone.
 3. An ionomer as defined in claim 1wherein monomer B comprises disodium3,3′-sulfonyl(4,4′-difluorobenzophenone).
 4. An ionomer as defined inclaim 1 wherein monomer C comprises 4,4′-difluorobenzophenone.
 5. Anionomer as defined in claim 1 wherein monomer A comprises4-(4-hydroxyphenyl)phthalazinone, monomer B comprises disodium3,3′-sulfonyl(4,4′-difluorobenzophenone), and monomer C comprises4,4′-difluorobenzophenone.
 6. An ionomer as defined in claim 1 whereinmonomer B comprises disodium 3,3′-sulfonylbis(4-fluorophenyl sulfone).7. An ionomer as defined in claim 1 wherein monomer C comprisesbis(4-fluorophenyl)sulfone.
 8. An ionomer as defined in claim 1 whereinmonomer A comprises 4-(4-hydroxyphenyl) phthalazinone, monomer Bcomprises disodium 3,3′-sulfonylbis(4-fluorophenyl sulfone), and monomerC comprises bis(4-fluorophenyl)sulfone.
 9. An ionomer comprising thereaction product of monomer A with monomer B and C in an azeotropingsolvent mixed with an inert aprotic polar solvent containing at least 2moles of an alkali metal base for each mole of monomer A, wherein themoles of monomers B plus C equal the moles of A, said reaction driven tocompletion by the azeotropic removal of water at a temperature above theazeotropic boiling point of the azeotroping solvent in the presence ofwater, wherein R₁₋₄ are independently H, linear or branched alkyl,aromatic, or halogen; X₁ and X₂ are independently a carbonyl or sulfoneradical or aromatic compounds connected through a ketone or sulfonelinkage; and Y is a halogen group.


10. An ionomer comprising the reaction product of monomer A with anionomer-contributing monomer.

wherein R₁₋₄ are independently H, linear or branched alkyl, aromatic, orhalogen.
 11. An ionomer as defined in claim 10 wherein saidionomer-contributing monomer comprises sulfonic acid.
 12. An ionomer asdefined in claim 10 wherein said ionomer-contributing monomer comprisescarboxylic acid.
 13. A sulfonated Poly(phthalazinone ether ketone)s,comprising repeating units of the polymers shown below:

wherein R₁ and R₂ are selected from hydrogen atom, alkyl group, oraromatic group and M is metallic base ion.
 14. A method of preparing asulfonated poly(phthalzinone ether ketone) comprising the steps of (a)copolymerizing 4,4′-dihalo(or dinitro)-3,3′-disulfonate salt ofbenzophenone, dihalo(or dinitro)benzophenone, and a monomer containingphthalazinone and phenol group, in polar solvents or reaction mediumcontaining mainly polar solvents, in the presence of a catalystcomprising a metallic base (or its salt), to obtain a product; (b)dehydrating said product at high temperature using azeotropicdehydration agents; (c) diluting said product with solvents; (d)coagulating said product using coagulation agents; (e) separating saidproduct; (f) drying said product; and (g) performing steps (c) through(f) two additional times to obtain said sulfonated poly(phthalazinoneether ketone).
 15. The preparation method of claim 14, wherein thereaction temperature is 150-220° C. and the reaction time is 4-32 hours.16. The preparation method of claim 14, wherein the polar solvents aredimethyl sulfoxide, tetramethylene sulfone, phenyl sulfone,1-methyl-2-pyrrolidinone, N,N-dimethylformamide.
 17. The preparationmethod of claim 14, wherein the azeotropic dehydration agents areselected from the group consisting of toluene, xylene, and chloroform.18. The preparation method of claim 14, wherein the coagulation agentsare water and one of the group of methanol and ethanol.
 19. A sulfonatedpoly(phthalazinone ether sulfone) comprising repeating units of thepolymers shown below:

wherein R₁ and R₂ are selected from hydrogen atom, C1-C4 linear orbranch alkyl group, or aromatic group, M is sodium or potassium ion,m+n.> or =20
 20. A method of preparing a sulfonated poly(phthalazinoneether sulfone), comprising the steps of (a) copolymerizing4,4′-dihalo(or dinitro)-3,3-disulfonate salt of phenyl sulfone,dihalo(or dinitro)phenyl sulfone, and a monomer containing phthalazinoneand phenol group, in polar solvents or reaction medium containing mainlypolar solvents, in the presence of a catalyst comprising a metallic base(or its salt), to obtain a product; (b) dehydrating said product at hightemperature using azeotropic dehydration agents; (c) diluting saidproduct with solvents; (d) coagulating said product using coagulationagents; (e) separating said product from said agents; (f) drying saidproduct; and (g) performing steps (c) through (f) two additional timesto obtain said sulfonated poly(phthalazinone ether sulfone).
 21. Thepreparation method of claim 20, wherein the monomer containingphthalazinone and phenol group has the following molecular structure:

wherein R₁ and R₂ are selected from hydrogen atom, C1-C4 linear orbranch alkyl group, or aromatic group.
 22. The preparation method ofclaim 20, wherein the reaction temperature is 140-220° C. and thereaction time is 1-36 hours.
 23. The preparation method of claim 20,wherein the polar solvents are dimethyl sulfoxide, tetramethylenesulfone, phenyl sulfone, 1-methyl-2-pyrrolidinone, andN,N-dimethylformamide.
 24. The preparation method of claim 20, whereinthe azeotropic dehydration agents are toluene, xylene, or chloroform.25. The preparation method of claim 20, wherein the coagulation agentsare water and methanol (or ethanol).
 26. A method for generatingelectricity comprising the steps of: (a) providing an anode; (b)providing a cathode; (c) providing a polymer electrolyte membranebetween said anode and said cathode and in communication with said anodeand said cathode, said polymer electrolyte membrane comprising theionomer of claim 1 in acid form (d) flowing a fuel to said cathode wheresaid fuel is disassociated to release a proton and an electron; (e)transporting said proton across said polymer electrolyte membrane tosaid anode; and (f) collecting said electron at a collector to generateelectricity.
 27. A method as defined in claim 26 wherein said polymerelectrolyte membrane comprises a polymeric support having interconnectedpassages and pathways that are substantially occluded by said polymer.28. A method as defined in claim 26 wherein said polymeric support isexpanded polytetrafluoroethylene.
 29. A method as defined in claim 26wherein said fuel is methanol.
 30. A method as defined in claim 26wherein said fuel is hydrogen.
 31. A method as defined in claim 27wherein said fuel is methanol.
 32. A method as defined in claim 27wherein said fuel is hydrogen.
 33. A method as defined in claim 28wherein said fuel is methanol.
 34. A method as defined in claim 28wherein said fuel is hydrogen.
 35. A polymer electrolyte membranecomprising the ionomer of claim 1 in acid form.
 36. A polymerelectrolyte membrane as defined in claim 35 further comprising apolymeric support having interconnected passages and pathways that aresubstantially occluded by said ionomer.
 37. A polymer electrolytemembrane as defined in claim 36 wherein said polymeric support isexpanded polytetrafluoroethylene.
 38. A membrane electrode assemblycomprising: (a) an anode; (b) a cathode; and (c) a polymer electrolytemembrane between said anode and said cathode and in communication withsaid anode and said cathode, said polymer electrolyte membranecomprising the ionomer of claim 1 in acid form.
 39. A membrane electrodeassembly as defined in claim 38 wherein said polymer electrolytemembrane comprises a polymeric support having interconnected passagesand pathways that are substantially occluded by said ionomer.
 40. Amembrane electrode assembly comprising: (a) an anode; (b) a cathode; anda polymer electrolyte membrane between said anode and said cathode andin communication with said anode and said cathode; wherein at least oneof said anode and said cathode comprises the ionomer of claim
 1. 41. Amembrane electrode assembly comprising: (a) an anode; (b) a cathode; and(c) a polymer electrolyte membrane between said anode and said cathodeand in communication with said anode and said cathode, said polymerelectrolyte membrane comprising the ionomer of claim 1 in acid form, (d)wherein said polymer electrolyte membrane has a relative selectivityfactor greater than 1.0.
 42. A membrane electrode assembly as defined inclaim 41 wherein said relative selectivity factor is about 1.3.
 43. Amembrane electrode assembly comprising: (c) an anode; (d) a cathode; and(c) a polymer electrolyte membrane between said anode and said cathodeand in communication with said anode and said cathode, said polymerelectrolyte membrane comprising the ionomer of claim 5 in acid form. 44.A fuel cell comprising the membrane electrode assembly of claim 38sandwiched between a first gas diffusion medium and a second gasdiffusion medium, said membrane electrode assembly being in electroniccommunication with a current collector.
 45. A fuel cell as defined inclaim 44 wherein said polymer electrolyte membrane comprises a polymericsupport having interconnected passages and pathways that aresubstantially occluded by said ionomer.
 46. A fuel cell as defined inclaim 45 wherein said polymeric support is expandedpolytetrafluoroethylene.
 47. A fuel cell as defined in claim 44 whereinsaid fuel cell is a direct methanol fuel cell.
 48. A fuel cell asdefined in claim 44 herein said fuel cell uses hydrogen as a fuel.
 49. Afuel cell as defined in claim 45 wherein said fuel cell is a directmethanol fuel cell.
 50. A fuel cell as defined in claim 45 wherein saidfuel cell uses hydrogen as a fuel.
 51. A fuel cell as defined in claim46 wherein said fuel cell is a direct methanol fuel cell.
 52. A fuelcell as defined in claim 46 wherein said fuel cell uses hydrogen as afuel.
 53. A fuel cell as defined in claim 44 having an open circuitpotential of 0.704 V.
 54. A fuel cell as defined in claim 44 having anaverage methanol crossover measurement of about 0.124.